Exhaust gas emitted from an internal combustion engine, particularly a diesel engine, is a heterogeneous mixture that contains gaseous emissions such as carbon monoxide (“CO”), unburned hydrocarbons (“HC”) and oxides of nitrogen (“NOx”) as well as condensed phase materials (liquids and solids) that constitute particulate matter. Catalyst compositions typically disposed on catalyst supports or substrates are provided in an engine exhaust system to convert certain, or all of these exhaust constituents into non-regulated exhaust gas components.
Particulate filters remove the particulate matter from the exhaust gas. The particulate matter accumulates within the particulate filter. Over time, the particulate filter becomes full and the trapped particulates must be removed. The trapped particulates are typically removed through a regeneration process that burns the particulates within the particulate filter. In some cases, if the heat from the regeneration process is too high, the particulate filter may become damaged.
Accordingly, it is desirable to provide methods and systems for selectively regenerating the particulate filter such that damage to the particulate filter does not occur.